Numerous welding systems and processes, involving corresponding equipment and devices, designed for a wide variety of uses and applications, such as in the manufacture of sheet metal, pipes, structural sections and parts with different materials and geometries in general, are known and extensively used in the prior art.
For the sake of completeness, and in order to introduce the characteristics and advantages of the present invention in the most appropriate way, the main known welding systems and processes will be briefly cited and commented on below.
TIG (Tungsten Inert Arc)
The TIG process exploits the heat produced by an electrical arc that jumps between a non-consumable electrode, in particular an electrode made of tungsten with other alloys, and the part to be welded; the weld pool is protected by a flow of gas or mixtures, with inert characteristics, which is conveyed by special ceramic nozzles.
The process can be used with or without filler metal, which in turn can be supplied from the exterior, either manually or by automated devices.
MIG/MAG (Metal Inert Gas or Metal Active Gas)
The MIG and MAG processes exploit the thermal energy supplied by an electrical arc that jumps between a consumable solid wire electrode, which is continuously fed axially in the welding area, and the part to be welded.
In said processes, the weld pool is protected by a continuous flow of gas mixtures conveyed by nozzles, wherein the type of gas mixture used defines the welding process: the process is called MIG when inert gases and mixtures are used, and MAG when active oxidising gases and mixtures are used.
Plasma
This welding process exploits the properties of a special state of matter, called “plasma”, which is generated in a gas by the passage of an electrical arc, strongly ionising the gas atoms so that they become capable of conducting energy.
FCAW (Flux-Cored Arc Welding)
This welding process, which exploits the characteristics of the MIG/MAG processes, involves the use of a tubular wire, made to advance axially, into which a particular chemical powder called “flux” is introduced.
The common denominator of all said processes is the use of a special welding instrument, commonly called a “welding torch” which, although it can vary physically according to the process performed, consists of a series of main components that perform the same or substantially similar functions.
It should be noted that in MIG/MAG and FCAW processes the filler material, in the form of a welding wire, is continuously fed by a feed guide fitted in the welding torch, whereas in TIG and plasma processes the filler material is fed manually, or through a device external to the torch.
For the sake of completeness, FIG. 7 shows a cross-section of a typical welding torch, indicated as TS, which is among those most commonly used, and in particular is designed for use in a MIG/MAG process, wherein the following main parts can be distinguished:
A Handle
B Insulator and threaded insert to guide filler wire
C Outer shroud or body
U Shielding gas nozzle
E Contact shoe between electrical conductor and filler wire guide
O Shielding gas passage
M Filler wire.
Regardless of the specific welding process in which it is used, the welding torch tends to accumulate welding residues and slag on its outer surface during use, which can reduce its efficiency and consequently that of the welding process.
The problem therefore arises of how to keep the torch free of the slag and residues that accumulate during the welding process for as long as possible, and how to remove said slag and residues from the torch, so as to continue using it, when the quantity accumulated on the welding torch reaches such a level as to prejudice its performance.
In the current state of the art and current practice, two main systems are used to keep welding torches clean and clean them of said welding slag and residues: one based on a chemical action and the other on a mechanical action.
In particular, the first system involves the use of anti-adhesive substances, usually contained in spray cans, which are sprayed on the parts of the welding torch before use and are designed to minimise the quantity of spatter, slag and residues that accumulate on the torch over time as a result of the welding operation.
Specifically, the method of use of this first cleaning system involves, before using the welding torch, dismantling the protective outer shroud or body of the torch, cleaning it of residues, and spraying its interior and the shielding gas nozzle with a film of anti-adhesive product.
In this way, the mechanical parts of the welding torch which are exposed to moisture are also protected against corrosion, with a reduction in wear on those parts caused by high temperatures or pressures.
Nevertheless, despite the application of said anti-adhesive substances, slag and residues tend to be deposited on the welding torch over time, though more slowly, with the result that after a certain period of use it is always necessary, at least in most cases, to remove the slag deposited on the body of the torch mechanically, using a cloth or pliers.
However, this first system has the drawback of needing a continuous supply of said spray cans, based on the workload of the torch, and is also onerous in terms of environmental impact, due to the high consumption of spray cans which must be disposed of, and the environmental emissions of the gases they contain.
The second cleaning system removes welding slag and residues from the welding torch by abrasive action, performed by a mechanical cutter.
This cleaning system, which is mainly used in automatic welding processes, has the drawback of considerably reducing the working life of the welding torch due to the abrasive action exerted on it; it also has the considerable limitation of only cleaning the terminal part of the shielding gas nozzle, while the interior of the nozzle, which has a larger diameter, and the filler wire guide, are never cleaned, with the result that welding deposits and slag accumulate there over time.
Consequently, even when this system requires removal of the outer shroud or shell of the torch before use, it cannot reach and clean the less accessible parts.
For the sake of completeness, it should be mentioned that the prior art includes welding torch cleaning systems and equipment which are based, at least in general, on the use of cold, and in particular use a jet or flow, formed by a cold fluid or a fluid at a relatively low temperature compared with ambient temperature, which is forcibly ejected against the torch to clean it.
The fluid used to form the cold jet can consist, for example, of carbon dioxide, supplied from a reserve where it is kept under pressure, which is caused to expand in the external environment at ambient pressure so that it cools and generates a flow containing solidified particles or pellets of carbon dioxide, called “dry ice”, which is directed against the welding torch to be cleaned.
When the solidified carbon dioxide particles collide with the surface of the torch, they perform a mechanical action that removes the welding slag and swarf deposited on that surface.
Said particles then sublimate or evaporate, after performing their mechanical action of swarf removal, so as to not leave any trace on the surface of the welding torch after cleaning.
In practice, this cleaning process has proved particularly effective to remove welding slag and swarf, due to the mechanical action performed by the solid particles contained in the flow of dry ice when they collide with the torch surface, and also presents the major advantage of not leaving residues on the welding torch after cleaning.
Examples of these systems, which use a cold jet or flow, formed by a fluid such as carbon dioxide at low temperature, to clean a welding torch, are described, for example, in granted American patent U.S. Pat. No. 6,732,955 B2 and published American patent application US 2008/0236633 A1.
However, said cold-cleaning systems, as described in said patent documents, appear, at least in general, to be fairly complex and inconvenient to use, whereas interested users, who may be tradesmen and/or small firms that only occasionally perform welding jobs, still need welding torch cleaning equipment which is simple, so as to require low maintenance, inexpensive, and above all easy and practical to use.
This rather complex construction, together with the low practicality of use of said known cleaning systems, in particular those using a flow of dry ice which is directed against the welding torch to clean it of slag, may at least partly explain why these cold-based systems have not yet been effectively used in industrial practice, despite their undeniable efficacy in removing welding slag and swarf and other substantial advantages connected with their use, such as the fact that they do not leave residues on the welding torch after cleaning.
In any event, regardless of the reasons for the non-use of said cold-based welding torch cleaning systems, at least at present, it should be emphasised that any improvement on them, in particular in terms of further improving their performance and practicality of use, is sure to be favourably received, because it is designed to meet the continual need for innovations, lower costs and more effective results in the field of maintenance and cleaning of welding torches.